5.7 英語マニュアルhttps://dev.mysql.com/doc/refman/5.7/en/create-index.html
An index_col_name specification can end with ASC or DESC. These keywords are permitted for future extensions for specifying ascending or descending index value storage. Currently, they are parsed but ignored; index values are always stored in ascending order.

[oracle@study01-mysql-1 ~]$ ./mysqlslap.sh
Benchmark
Running for engine InnoDB
Average number of seconds to run all queries: 38.711 seconds
Minimum number of seconds to run all queries: 38.711 seconds
Maximum number of seconds to run all queries: 38.711 seconds
Number of clients running queries: 10
Average number of queries per client: 10000
[oracle@study01-mysql-1 ~]$

[oracle@study01-mysql-1 ~]$ ./mysqlslap.sh
Benchmark
Running for engine InnoDB
Average number of seconds to run all queries: 38.466 seconds
Minimum number of seconds to run all queries: 38.466 seconds
Maximum number of seconds to run all queries: 38.466 seconds
Number of clients running queries: 10
Average number of queries per client: 10000
[oracle@study01-mysql-1 ~]$

[oracle@study01-mysql-1 ~]$ ./mysqlslap.sh
Benchmark
Running for engine InnoDB
Average number of seconds to run all queries: 185.845 seconds
Minimum number of seconds to run all queries: 185.845 seconds
Maximum number of seconds to run all queries: 185.845 seconds
Number of clients running queries: 10
Average number of queries per client: 50000
[oracle@study01-mysql-1 ~]$

抜粋：
READ_BACKUP: Setting this option to 1 has the same effect as though ndb_read_backup were enabled; enables reading from any replica.
Setting this option to 1 automatically sets FRAGMENT_COUNT_TYPE to ONE_PER_LDM_PER_NODE_GROUP (see next item).
Starting with MySQL Cluster NDB 7.5.3, you can set READ_BACKUP for an existing table online,
using an ALTER TABLE statement similar to one of those shown here: